This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Reciprocating compressors are frequently used to compress and transport fluids, such as natural gas. Generally, a reciprocating compressor includes a piston and a cylinder. During compression, inlet valves temporarily open to allow the fluid to flow into the cylinder. Then, the inlet valves close, and the piston is driven through the cylinder, reducing the volume of the cylinder in which the fluid is disposed and elevating the pressure of the fluid. The change in the volume of the cylinder during the compression stroke of the piston is referred to as the “swept volume.” Near the end of the piston's travel, an outlet valve is opened and the compressed fluid flows from the cylinder.
Compressors are often characterized by their volumetric compression efficiency. This parameter is the ratio of the swept volume to the total volume of the cylinder that houses the fluid being compressed. A high volumetric efficiency generally correlates with a larger outlet pressure, as a substantial portion of the volume of the cylinder is swept by the piston, and a low volumetric efficiency generally correlates with a lower outlet pressure, as the percentage reduction in the cylinder's volume during a piston stroke is lower.
The volumetric compression efficiency of a given compressor may not be matched to the system in which the compressor operates. A compressor design may be used in a variety of systems that expose the compressors to different conditions. For example, across systems, the compressor may be subject to varying inlet pressure or outlet pressure, as components upstream or downstream from the compressor may impede flow to or from the compressor to differing degrees in different applications. These variations and others can affect the performance of a compressor. Accordingly, it would be useful to be able to tune a compressor's volumetric compression efficiency according to characteristics of upstream and downstream components.